Usually I price at what will sell it faster than what its on the boards for, regardless of history and ethics or morals.

For example... a while back Heavens Eye Materia II were selling for 5k on Goblin... I sold all of mine for 4795. 205 gil cheaper. I don't really care about how much gil I lost because I put no investment into getting these materia. Is that considered undercutting? sure. Do I care what someone else sitting on the MB all day trying to "play the market" thinks? Not at all. Should I care? Its a video game auction hall... so no.